Quantum initial condition sampling for linearized density matrix dynamics: Vibrational pure dephasing of iodine in krypton matrices

TL;DR

This paper presents an efficient quantum initial condition sampling method using the Feynman-Kleinert harmonic approximation to accurately model vibrational pure dephasing of iodine in krypton matrices, outperforming classical sampling at low temperatures.

Contribution

It introduces a quantum initial condition sampling technique based on the Feynman-Kleinert approximation for linearized density matrix dynamics, improving accuracy over classical methods.

Findings

Quantum sampling yields faster dephasing rates consistent with experiments.

Classical sampling significantly underestimates dephasing rates at low temperatures.

The method enhances the accuracy of vibrational dephasing simulations.

Abstract

This paper reviews the linearized path integral approach for computing time dependent properties of systems that can be approximated using a mixed quantum-classical description. This approach is applied to studying vibrational pure dephasing of ground state molecular iodine in a rare gas matrix. The Feynman-Kleinert optimized harmonic approximation for the full system density operator is used to sample initial conditions for the bath degrees of freedom. This extremely efficient approach is compared with alternative initial condition sampling techniques at low temperatures where classical initial condition sampling yields dephasing rates that are nearly an order of magnitude too slow compared with quantum initial condition sampling and experimental results.